Are you a TrendMiner admin and did you receive an email with subject "TrendMiner restart required" containing the following message, then this post might interest you:

Dear administrator,

The internal cluster certificates of your TrendMiner installation are about to expire within 90 days.
Please reboot TrendMiner to refresh the certificates.

Kind regards,
TrendMiner

Why did you get this email?

The TrendMiner appliance internally uses certificates to secure the communication between the different microservices. Similar to regular TLS certificates which you upload to secure the communication between the users’ computers and the TrendMiner server, these internal certificates also expire after a while and need to be renewed.

In contrast to the TLS certificates which secure client-server traffic and which need to be renewed by the TrendMiner server admin explicitly, the internal cluster certificates are renewed automatically by the server when the server is rebooted.

If you received the above email this indicates your server was recently not rebooted and needs to be rebooted within 90 days to avoid the internal certificates to expire.

What happens if you do not reboot in time?

If you do not reboot in time the certificates will expire and some functionality will stop working. The most common symptoms of expired certificates are failures during database backup creation and failing TrendMiner upgrades.

How to recover from expired certificates?

To recover from expired certificates, please contact TrendMiner support who will invite you for a call to run some commands via the console.

Please note that if you regularly upgrade TrendMiner you will never get these emails as the TrendMiner server is rebooted during the upgrade process (in case you are running a virtual appliance). For single node deployments the server should be rebooted manually after updating the OS/system packages. 

So to be in line with our lifecycle policy we strongly advise to always upgrade TrendMiner to a supported version.